Cellulases or cellulytic enzymes are enzymes involved in hydrolyses of cellulose. In the hydrolysis of native cellulose, it is known that there are three major types of cellulase enzymes involved, namely cellobiohydrolase (1,4-β-D-glucan cellobiohydrolase, EC 3.2.1.91), endo-β-1,4-glucanase (endo-1,4-β-D-glucan β-glucanohydrolase, EC 3.2.1.4) and β-glucosidase (EC 3.2.1.21).
Cellulases are synthesized by a large number of microorganisms which include fungi, actinomycetes, myxobacteria and true bacteria but also by plants. Especially endoglucanases of a wide variety of specificities have been identified.
A very important industrial use of cellulytic enzymes is the use for treatment of cellulosic textile or fabric, e.g. as ingredients in detergent compositions or fabric softener compositions, for bio-polishing of new fabric (garment finishing), and for obtaining a “stone-washed” look of cellulose-containing fabric, especially denim, and several methods for such treatment have been suggested.
An object of the present invention is to provide novel enzyme preparations having substantial cellulytic activity at acid or neutral conditions and improved performance in paper pulp processing, textile treatment, laundry processes or in animal feed; preferably novel cellulases, more preferably well-performing endoglucanases, which are contemplated to be producible or produced by recombinant techniques.
Most newly manufactured cotton fabrics and cotton blend fabrics have a handle that is rather hard and stiff unless they are treated with finishing components. Furthermore, the fabric surface is not always smooth due to small fuzzy fibers protruding from the individual cotton fibers. In addition, after a relatively short period of wear, collections of lint appear on the surface (surface linting) giving the appearance of “pills” on the surface which causes the fabric to have an unappealing, worn look. In polyester fabrics, this phenomena is actually “pilling” and provides a similar unappealing fabric appearance. The term “pilling” will also apply to cellulosic fabrics in the instant application.
Thus, a useful feature of cellulases in the treatment of textiles is their ability to recondition used fabrics by making their colors more vibrant. For example, repeated washing of cotton containing fabrics results in a greyish cast to the fabric which is believed to be due to disrupted and disordered fibrils, sometimes called “pills”, caused by mechanical action. This greyish cast is particularly noticeable on colored fabrics. As a consequence, the ability of cellulase to remove the disordered top layer of the fiber and thus improve the overall appearance of the fabric has been of value.
Cellulase treatment of the fabric surface improves fabric quality with respect to handle and appearance without loss of fabric wettability. The most important effects are less fuzz and pilling, increased gloss/luster, improved fabric handle, increased durable softness and improved water absorbency. These effects are referred to as biopolishing effects.
Despite knowledge in the art related to many cellulase compositions, there is a continued need for new cellulases having a varying spectrum of characteristics which are useful in, for example, treating textiles, as a component of detergent compositions, in the treatment of pulp and paper, and in the conversion of biomass.
The cellulase compositions described herein provide improved performance characteristics, especially in textile processing.